i have a '97 xk8 (very recently aquired) it starts fine when its cold. but after say 20-30 mins driving it wont re-start. it runs a system check and the display says "fail safe engine mode" it will turn over but wont fire.
i had a diagnostics check today but no faults are showing on the ecu but it happened again today
any advise would b much appreciated

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Hiya,

Check and replace if required the Crankshaft Sensor.

Supertrev  .

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After battling engine start problems, engine shutoff while driving, and finally engine no-start (fortunately while still in my garage), I decided to open up the Engine Control Module (ECM) to see whether there was anything obvious that I could pin the problems on.

I had previously replaced the Throttle Body (TB) with a new one due to engine shut-offs while driving, hard starts, etc. I suspected the Throttle Position Sensor (TPS), but it cannot be purchased separately. This solved problems for about a year.

I also checked for loose connector plugs and pins, which has happened with plugs under the TB as well as one of the plugs on the side of the TB.

I checked for loose relays. Peviously, I had the starter relay shake loose which I solved by bending the spades for a tighter fit.

I checked all of the fuses. All OK.

So what is left? Since I had previously replaced the Drivers Door Control Module (DDCM) and the TB due to faulty electronics, why not suspect the ECM? I knew that it would cost me multiple $1000's to have the car flatbedded to a dealer 2 hours away, pay hourly rates for diagnostics and repairs, and exorbitant parts prices. And since I have previously taken apart my home computers to change or recycle parts, opening up the ECM should be no more difficult.

The ECM is easy to get to. Remove the plastic panel on the right hand side of the engine bay that "protects" the delicate electricals and electronics underneath. Remove the control module bay cover, remove the smaller Transmission Control Module (TCM) vertically mounted towards the front, disconnect the cables to the ECM, and slide it out and up. Now remove the ECM cover to expose the brains of engine management and the root of so many problems in modern cars.

Sure enough, after hinging up the top circuit board and using a magnifying glass, I found a couple of capacitors that possibly overheated, leaked some goo out, and corroded the circuitry. I purchased replacement capacitors on-line from Digi-Key for about $0.30 each and soldered them in, using some hammered flat copper wire to replace the circuits. I replaced the ECM but no luck firing up the engine. There might be additional damage that I could not find.
Next I sent the ECM to GoECM.com in Grand Prairie, Texas. For $575 + $20 shipping they repaired the ECM and sent it back to me. I plugged it in and ... the engine fired up immediately. It has now been running a couple of months without fault. And a prior problem that I had with the cooling fans inappropriately cycling on-off with the A/C has also been resolved.

The technician's report is as follows:
"Faulty aluminum electrolytic capacitors. Electrolytes caused corrosion and discontinuity throughout board. Re-traced signals. Replaced faulty resistors and diodes. Corrosion caused failing of multifunction IC's. Replaced. Tested~~>OK."
You can battle these electronic gremlins for years, pay $1000's to a repair facility for parts and labor, and you still might not have the problems solved. But this is an easy check that you can make yourself which might save you a lot of money, time, and aggravation!